The use of so-called smart drugs is growing in popularity. But do they work?

It was a normal Tuesday morning when my friend first told me about "smart drugs".

"Everyone does it. They're just pills that make you concentrate," she explained. She was taking them to deal with her "big day" ahead.

Many so-called smart drugs have conventional uses - a popular one, modafinil, is used to treat excessive need for sleep caused by narcolepsy or shift work. But they are also being taken, in growing numbers, by people looking to work more effectively.

Modafinil was dubbed the "world's first safe smart drug" by researchers at Harvard and Oxford universities who suggested its effects were "low risk" when taken in the short term. But side effects can include insomnia, headaches and potentially dangerous skin rashes, and there is a lack of long-term data.

Nevertheless, having read such positive reviews online - some claiming smart drugs had drastically improved their university grades - I decided to take it as an experiment.

While it is illegal to sell modafinil in the UK without a prescription, it is not illegal to buy. There are many websites, often based in India, which make it available to purchase - though the UK's Medicines and Healthcare Products Regulatory Agency warn this can be unsafe.

When the package arrived less than a week later, the drugs looked similar to paracetamol tablets.

After consulting a doctor - who said, being young and healthy, it was unlikely I'd have severe side effects - I decided to go ahead.

I took the first pill at the University of Cambridge as part of a cognitive test, where they examined my visual sustained attention, spatial working memory, executive function and episodic memory before and after taking the drug.

Prof Barbara Sahakian was confident the pill would have an effect: "We've done a number of studies that show an increase in cognitive ability when taken - from doctors doing night shifts to healthy people in a controlled testing environment."

Before the pills, my attention was in the top 15-20% of people my age. After, it was in the top 5-10%.

I had certainly begun to feel more awake, and a bit less prone to frustration having taken the drug. But there were a number of other factors that could have affected the results.